And I stood upon the sand of the sea, and saw a beast rise up out of the sea,
having seven heads and ten horns, and upon his horns ten crowns,
and upon his heads the name of blasphemy.
Revelation 13:1
The Number of the name of the beast has to be one of blasphemy.
Two things are specified in scripture as blasphemy-
1) Claiming power to forgive sins
2) Claiming to be God on earth
* Head of the Papal Institution, known as the so-called "Holy Father in Rome", has just that name for a title - Vicarius Filii Dei (Latin: Vicar or Representative of the Son of God)
* This institution also claims to be able to forgive sins (penance, going to the confessional, attending mass, last rites, etc.)
It is insulting when those who mock this by saying you can get 666 from many names. But those names don't fulfill the characteristics of the Little Horn of Daniel, Beast of Revelation or claim to be God's personal Vicarius Filii Dei on earth or the power to forgive sins. Only one does....